"The ignition of the Russia/Ukraine situation has created the bid," said Tom Tucci, head of U.S. Treasury trading at CIBC World Markets, in an emailed note to clients shortly after noon. "Massive short covering in the last hour after yesterday's real money buying."

The release of mixed February U.S. retail sales data at 8:30 AM ET this morning caused Treasuries to drop briefly, sending yields slightly higher. The U.S. dollar strengthened a bit against the euro and the Japanese yen as well.

However, these moves were completely erased two hours later, and the dollar is now down 1.1% against the yen, trading around ¥101.60.

European indices closed deep in the red across the board. The German DAX took the worst of it, falling 1.9%. Peripheral government bond yields in Italy, Spain, Portugal, and Greece are rising.

Russia's MICEX equity index closed down 2%, and yields on local-currency government debt rose in Thursday trading. The Russian ruble is losing ground against the dollar.

The charts below show movements in various markets. Across the top from left to right are S&P 500 futures, the U.S. dollar-Japanese yen exchange rate, and the euro-U.S. dollar exchange rate. Across the bottom are gold futures, 10-year U.S. Treasury futures, and December 2015 eurodollar futures.